Multi-polarized loop antenna array electromagnetically coupled to spaced transmission line



Jan. 25, 1966 R. J. STE GEN 3,231,891

MULTI-POLARIZED LOOP ANTENNA ARRAY ELECTROMAGNETICALLY COUPLED TO SPACED TRANSMISSION LINE Filed Dec. 25, 1961 INVEN TOR. fiaas/er .S'raaav A TTOR/VE) United States Patent I,

3,231,891 MULTI-POLARIZED LOOP ANTENNA ARRAY ELECTROMAGNETICALLY COUPLED T SPACED TRANSMISSION LINE Robert J. Stegen, Van Nuys,'Calif., assignor to Canoga Electronics Corporation, Van Nuys, Califl, a corporation of Nevada Filed Dec. 26, 1961, Ser. No. 162,122 6 Claims. (Cl. 343-742) The present invention relates to new and improved antenna systems. More particularly, the invention relates to antenna arrangements comprising multiple conductor transmission lines which areelectromagnetically coupled to surrounding transmitting or receiving loop arrays to effect systems that may operateto propagate radiant energy in multi-polarized field patterns or to receive radiant energy propagated in such patterns.

While there are many antenna constructions presently in use which may be operated to disperse electrical signals in dependable field patterns in polarized orientation,

. Patented Jan. 25, 1966 13 and 14 of relatively small diameter. Each of conductors 11 to 14 is encircled by one of conductive loops 15, 16, 17 and 18, which are connected to the central conductor to form symmetrically disposed horizontal cloverleaf arrays. A plurality of similar arrays is lon- 1 gitudinally spaced along the length of the transmission none of them is capable of the flexibility aiforded by I the present invention which provides a simplemeans by which the radiant energy within the propagated field may be directionally polarized along different axes. or polarization patterns.

This feature of the inverltitini's very useful in that single antennas or transmitting and receiving equipment may be utilized for different transmission or receiving requirements. Additionally, this concept may be utilized as a means of effecting separation of information on a fixed carrier frequency. For example, it is recognized that variations in the proximity of an antenna to the earth greatly atfect its ability to send or receive radiant energy of different polarizations where appreciable distances are involved. Since antennas close to the ground are most effective when vertical polarization is employed and those disposed at a high altitude are most effective when horizontal polarization is utilized, it would be desirable to be afforded of a single piece of equipment that could readily be converted to operate in the presence of the most effective type of polarization.

Accordingly, it is a broad object of the present invention to provide an antenna system that can be employed to elficiently handle multi-polarized radiant fields.

Another object of the invention is the provision of an antenna whose polarization may be changed or sensed through the expedient of electromagnetic coupling.

Still another object of the invention is the provision of antennas systems wherein changes in polarization of radiant energy fields are elfected by means of electromagnetic coupling to transmitting or receiving equipment.

Further objects and additional advantages of the invention will become apparent to those skilled in the field to which it pertains from a consideration of the following detailed description and drawing.

FIG. 1 is a cross-sectional view of one embodiment of the invention.

FIG. 2 is a cross-sectional view taken along line 22 in FIG. 1.

FIG. 3 is a cross-sectional view of another embodiment of the invention.

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3.

In the drawing, like reference characters designate similar parts in the several views.

As shown in FIG. 1, one embodiment of the present invention comprises a transmission line including a central conductor 10 of relatively large cross-sectional area and four equally spaced surrounding conductors 11, 12,

line.

Current flow is induced in each of the loops 15 to 18 by means of electromagnetic coupling between the individual loops and the centrally positioned conductors 11to 14 with which the loops are associated in response to current flow in each of the central conductors. Such flow of current in the loops is of appreciable magnitude upon a condition of resonance in the loops. Resonance may be achieved by making the circumferential length of each loop approximately equal to the wave length of the transmission line carrier frequency.

Th radiant fields associated with each cloverleaf array may be suitably polarized by appropriately phasing the currents induced in the individual loops 15 to 18 of the array. For example, if it is desired to produce a horizontally polarized radiant field the current flows in the four conductors 11 to 14 are so phased as to produce a current flow difference of in opposite loops. When several arrays are spaced longitudinally along the transmission line, as'shown in FIGS. 1 and 2, a narrow horizontally polarized beam is produced along the axis of the larger central conductor.

A modified form of an antenna utilizing the principles of the invention is shown in FIGS. 3 and 4. Here, each array is formed by a conductive ring 20 which is provided with radially extending conductive rods 21, 22, Band 24 which are connected at their inner ends to the central conductor 10 of a transmission line identical to that shown in FIG. 1 and which includes the similarly spaced smaller conductors 11 to 14. The closed loops are formed by the conductive paths defined by two adjacent rods, such as 21 and 22, for example, and the portion of ring 20 connecting their outer ends. It is to be understood that adjacent closed loops comprise common rods as part of their conductive paths.

It is to be noted that the conductors 11 to 14 are equally spaced between adjacent conductive rods and that each set of rods and rings 20 forming an array, best described as a wagon wheel array, are disposed in a horizontal plane.

This form of antenna performs in the same manner as that described in conjunction with FIGS. 1 and 2.

It is to be understood that the large central conductor 10, alone or in combination with conductors 11 to 14 of the antenna may also be utilized with conventional insulating members disposed at each end to provide a supporting structure for the antenna. Also, while not shown, the conductors 10 to 14 comprising the transmission line may be held in position by conventional spacing insulators.

Each antenna array of the above described modifications may be used to produce radiant field patterns which are either of dual linear polarization or circular in either direction by suitably switching between lines 11 to 14. It is to be understood that the switching operation may be effected by a transmission line network. For example, in the case of linear horizontal polarization, opposite conductors 12 and 14 and their respective loops, in the case of a coaxial feed line, would be connected together by means of a conventional matched T junction and a dilferenti-al line length of a half wave length. The T junction would split the power equally, the 180 line length would reverse the currents on the two conductors 12 and 14 so that the resulting radiation from the two loops would reinforce each other in the direction normal to the lane of the loop arrays.

To provide vertical polarization, conductors 11 and 13 and their respective loops would be connected in a similar manner. Switching between the input to the T junction of conductors 11 and 13 and the input to'the T junction of conductors 12 and 14 would result in switching between vertical and horizontal polarization. If the inputs to these two T junctions are connected to a third T junction by means of two lines which differ in length by a quarter wave length, 90, the resulting radiation would be circular. The direction, orhandedness, of the circular polarization depends upon which line is longer than the other.

From the foregoing it should be apparent to one skilled in the art that the present invention provides antenna constructions that may be energized from conventional transmitting equipment in the manner described to pro vide a radiant field of desired polarization. Also, such antennas may be used to receive similarly polarized signals.

While specific embodiments of the present invention have been disclosed in the foregoing description, it will be understood that various modifications Within the spirit of the invention may occur to those skilled in the art. Accordingly, it is intended that no limitation be imposed on the invention except as defined by the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. An antenna system including a planar array comprising a plurality of closed conductive loops each connected at a point on their periphery to a central conductor, and a coaxially disposed mechanically spaced conductor extending through each of said loops.

2. An antenna system including a transmission line comprising a central conductor and a plurality of adjacent conductors disposed parallel to said central conductor, said adjacent conductors being equally spaced radially from said central conductor, a planar array disposed on said line comprising a conductive loop coaxially surrounding each of said adjacent conductors in spaced relation and having a point on the periphery thereof conductively connected to said central conductor.

3. An antenna system according to claim 2 wherein said transmission line is provided with a plurality of said arrays at spaced intervals along said line.

4. An antenna system comprising an elongated central conductona plurality of adjacent mechanically separated conductors extending parallel to said central conductor and spaced therefrom, a radiating array comprising a spaced loop of conductive material coaxially encircling said conductors, and conductive rods extending between spaced points on said loop and said central conductor.

5. An antenna system according to claim 4 wherein each one of said rods extends centrally between adjacent pairs of said adjacent conductors.

6. .An antenna system as defined in claim 5 wherein a plurality of said arrays is disposed at spaced intervals along said conductors.

References Cited by the Examiner UNITED STATES PATENTS 2,521,550 9/1950 Smith 343742 2,665,380 1/1954 Hickson et al 343-809 X 2,818,562 12/1957 Carter 343---742 OTHER REFERENCES Forbes: An End Fire Array Continuously Proximity- Coupled: ASTIA ad No. 234,385, December 1959, pages 1-6 and 9.

ELI LIBERMAN, Acting Primary Examiner. 

2. AN ANTENNA SYSTEM INCLUDING A TRANSMISSION LINE COMPRISING A CENTRAL CONDUCTOR AND A PULARITY OF ADJACENT CONDUCTORS DISPOSED PARALLEL TO SAID CENTRAL CONDUCTOR, SAID ADJACENT CONDUCTORS BEING EQUALLY SPACED RADIALLY FROM SAID CENTRAL CONDUCTOR, A PLANAR ARRAY DISPOSED ON SAID LINE COMPRISING A CONDUCTIVE LOOP COAXIALLY SURROUNDING EACH OF SAID ADJACENT CONDUCTORS IN SPACED RELATION AND HAVING A POINT ON THE PERIPHERY THEREOF CONDUCTIVELY CONNECTED TO SAID CENTRAL CONDUCTOR. 